The present invention pertains to an apparatus for sizing a bolt to a desired length. In particular, the apparatus of the present invention shears a bolt to a desired custom length, Producing lead threads on the end of the bolt that are ready for use. Although bolts are available in a variety of standard pre-cut lengths (e.g., xc2xdxe2x80x3, xc2xexe2x80x3, 1xe2x80x3, 1xc2xdxe2x80x3) and such standard lengths are usually suitable for most application, the apparatus of the present invention allows sizing of a bolt to Any desired custom length. The apparatus of the present invention also allows use of the bolt immediately after sizing, without the need for any secondary finishing process.
It is generally known to use grinding wheels and other similar cutting tools to cut or otherwise size a bolt or other mechanical fastener to a desired length. However, such methods are not ideal solutions in all cases. Often times, heat generated in a grinding process may tend to anneal a hardened bolt, thereby degrading its strength. Although coolants may be used to control the amount of generated heat, such coolants must be contained. The use of fluid coolants also tends to be messy and not worth the trouble for small jobs. Also, both the bolt and the cut-off end may be dangerously hot from the grinding or other cutting operation, such that the bolt may not be safely usable for some period of time. Such processes may also cause undesirable discoloration of the bolt or potentially dangerous smoke and sparks.
There are other inherent problems in using conventional cutting tools for sizing a bolt to length. Cutting operations can be relatively time consuming. For example, in grinding, the processing time can be influenced by several factors including the type and size of the grinding wheel, the speed of rotation of the grinding wheel, the speed of advancement of the grinding wheel through the cut, and the material of the bolt. Also, there is usually a fair amount of set-up time involved in preparing a cutting tool for a sizing operation. For instance, in the case of a conventional rotary cut-off tool, a suitable grinding wheel must be mounted and the bolt must be properly secured relative to the wheel to allow its proper sizing. In many cases, there is also a fair amount of skill involved in cutting a bolt to ensure that its end is square that its lead threads are not damaged. Additionally, in some cutting operations, burrs may be formed on the end of the bolt, which must be removed through a secondary finishing operation before use.
As an alternative to using a grinding wheel, smaller diameter bolts may be sheared to a desired length with other conventional cutting tools. However, in shearing, care must be used to ensure the lead threads at the bolt end are not damaged. If lead threads are damaged, the user must either discard the damaged bolt entirely or use a special die to re-cut the threads, which takes some measure of skill. Also, in shearing, care must be used to ensure the cut is as clean as possible without producing burrs on the end of the bolt, which may interfere with the bolt""s engagement in a tapped hole or nut. Typically, bolts are made from hardened steel material, and any burrs formed during a sizing process can be difficult and time consuming to remove in secondary finishing operations, such as filing, grinding or sanding. The prior art does include hand tools intended for use in shearing bolts. However, in many cases, such hand tools are difficult to use, because such bolt-shearing operations, by their very nature, require a fair amount of force and proper securement of the bolt to achieve a clean cut without causing deformation of the bolt or damage to the lead threads.
Thus, there is a need for a hand held bolt cutting tool that can be used to shear a bolt to a desired custom length, producing lead threads on the end of the bolt that are ready for use, without the need for any secondary finishing process.
It is therefore an object of the present invention to provide a device for quickly and easily producing a ready to use bolt at a desired custom length without causing deformation of the bolt or damage to its lead threads. The apparatus of the present invention avoids many of the problems found in conventional grinding, sawing and cutting operations and provides a means for cutting commonly sized bolts for most any type of job.
In general, a bolt cutting tool of the present invention comprises a bolt engaging portion and a cutting blade. The bolt engaging portion has at least one bolt-receiving bore, which is adapted for receiving a portion of a bolt to be cut. The cutting blade is rotatably connected to the tool generally adjacent the bolt engaging portion. The cutting blade has a cutting surface with an arcuate peripheral cutting edge. The cutting blade is adapted for rotation relative to the bolt-receiving bore from a pre-cut starting position toward a post-cut finishing position. The blade is adapted to rotate in a manner so that the arcuate peripheral cutting edge of the blade cuts the bolt as the cutting blade is rotated toward the post-cut finishing position. The blade is configured so that an angle of incidence between the cutting surface of the blade and a center axis of the bolt-receiving bore is less than 15 degrees when the blade is in its pre-cut starting position.
In another aspect of the invention, the arcuate peripheral cutting edge of the cutting blade has a cut initiating portion and a cut finishing portion. The cut initiating portion of the arcuate peripheral cutting edge is adapted for initial engagement with a bolt received in the bolt-receiving bore when the cutting blade is in its pre-cut starting position. The cut finishing portion of the arcuate peripheral cutting edge is adapted for engagement with the bolt when the cutting blade is rotated toward its post-cut finishing position. The arcuate peripheral cutting edge has a radius of curvature that increases as the cutting edge extends from its cut initiating portion toward its cut finishing portion. The radius of curvature of at least a portion of the arcuate peripheral cutting edge increases at a rate that is greater than a constant rate as the cutting edge extends toward its cut finishing portion.
In still another aspect of the invention, a bolt cutting tool comprises a bolt engaging portion and a cutting blade rotatably connected to the tool generally adjacent the bolt engaging portion. The bolt engaging portion has at least one bolt-receiving bore with an internally threaded portion. The internally threaded portion is adapted for threaded engagement with an externally threaded bolt to be cut. The internally threaded portion of the bore defines a major inside diameter of the bore and a minor inside diameter of the bore. The major inside diameter is larger than the minor inside diameter. The cutting blade has a cutting surface with an arcuate peripheral cutting edge. The blade is adapted for rotation relative to the bolt-receiving bore from a pre-cut starting position toward a post-cut finishing position. The blade is adapted for rotation in a manner so that the arcuate peripheral cutting edge of the blade cuts the bolt as the cutting blade is rotated toward, the post-cut finishing position. The arcuate peripheral cutting edge lies within a plane that is generally perpendicular to an axis of rotation of the cutting blade. An end portion of the bore adjacent to the plane is counterbored to a diameter larger than the minor inside diameter.
While the principal advantages and features of the present invention have been described above, a more complete and thorough understanding and appreciation of the invention may be attained by referring to the drawings and detailed description of the preferred embodiments, which follow.